Security readout for executives and security teams
Plain-English summary
A Linux AppArmor parsing error can read beyond a memory buffer while checking file-access policy. A local, low-privileged user may be able to trigger it without user interaction. The supplied CVSS assessment rates potential confidentiality, integrity, and availability impacts as high, although practical compromise is not demonstrated.
Executive priority
Treat this as a high-priority kernel update for multi-user Linux estates and systems offering local access to untrusted users. Schedule remediation through normal emergency or accelerated patching processes. Internet-facing status alone does not establish exposure because the documented attack vector is local.
Technical view
The match_char() macro evaluates its character argument repeatedly. When called with *str++, each evaluation advances the pointer, skips input characters, and can move beyond the buffer. KASAN observed a one-byte slab out-of-bounds read in aa_dfa_match during AppArmor file-open permission processing. The fix evaluates the character once before invoking the macro.
Likely exposure
Exposure concerns Linux systems using an affected kernel with AppArmor involved in path-permission checks, especially multi-user or hosted systems permitting untrusted local access. The supplied metadata lists multiple kernel branches but does not clearly define every affected and fixed range; verify exact distribution packages through vendor guidance.
Exploitation context
The CVSS vector describes a local, low-complexity attack requiring low privileges and no user interaction. The bundle reports no CISA KEV listing and provides no evidence of active exploitation or a public weaponized exploit. The KASAN trace demonstrates the out-of-bounds read, not reliable privilege escalation or full system compromise.
Researcher notes
The strongest evidence is a KASAN-detected one-byte slab out-of-bounds read in aa_dfa_match reached through AppArmor file-open processing. The CVSS impact claims are severe, but the bundle does not establish exploitability beyond the read, controlled data disclosure, memory corruption, privilege escalation, denial of service, or exploitation in the wild.
Mitigation direction
- Update to a distribution kernel incorporating the linked upstream or stable AppArmor correction.
- Use vendor advisories to identify the corrected package for each deployed kernel branch.
- Prioritize multi-user systems where untrusted users have local access.
- Restrict unnecessary local access until patched, where operationally feasible.
Validation and detection
- Inventory kernel versions and determine whether AppArmor is enabled and enforcing.
- Map each kernel package to vendor advisories or the linked stable fix commits.
- Confirm the installed kernel contains the single-evaluation match_char correction.
- After updating, reboot into the corrected kernel and verify AppArmor enforcement remains healthy.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2026-23406 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9LinuxVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/c7dc56d8b37eda1396feeec3ab1c7ecee5eae31bCVE reference, Linux
- https://git.kernel.org/stable/c/f16f2e5936c0f5f0d11fdf10d2be3e47e7108e42CVE reference, Linux
- https://git.kernel.org/stable/c/1fc94f16098213d01e56c97feed9b3ecf0147a37CVE reference, Linux
- https://git.kernel.org/stable/c/5a184f7cbdeaad17e16dedf3c17d0cd622edfed8CVE reference, Linux
- https://git.kernel.org/stable/c/b73c1dff8a9d7eeaebabf8097a5b2de192f40913CVE reference, Linux
- https://git.kernel.org/stable/c/0510d1ba0976f97f521feb2b75b0572ea5df3cebCVE reference, Linux
- https://git.kernel.org/stable/c/383b7270faf42564f133134c2fc3c24bbae52615CVE reference, Linux
- https://git.kernel.org/stable/c/8756b68edae37ff546c02091989a4ceab3f20abdCVE reference, Linux
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.